Spatial Neglect and Attention Networks

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Spatial Neglect andAttention Networks

• Youngjin Kang
• Baoyu Wang
• Zhiheng Zhang

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20. Figure 5a

• Posner task Attention reorienting
• Both TPJ and VFC showed contralesional deficits
• VFC also showed reorienting deficits in the
  ipsilesional field

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20. Figure 5b

• Detection of behaviorally relevant stimuli
• Detection deficits in neglect patients
• Lager TRs to an ipsilesional auditory stimulus

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20. Figure 5c

• Arousal deficits in neglect patients
• TPJ patients showed a vigilance decrement

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21. It seems odd that arousal and neglect are
connected. What is the nature of the connection?
What hemispheric phenomena are involved?

• Right hemisphere injury patients have lower
  arousal than left injury patients
• An impairment of ability to sustain the arousal
• Auditory counting test of arousal in neglect
  patients indicated a strong linkage between
  arousal and spatial deficits
• Arousal related activations are associated in the
  ventral frontoparietal cortex

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22.So what to the authors believe about these
issues concerning right hemisphere lateralization
and the physiology of core non-spatial deficits?
Tie together the other symptoms in neglect and
the core deficits.

• Reorienting of attention
• Neuroimaging studies of healthy adults have shown
  that reorienting to stimuli in either visual
  field that are presented outside the focus of
  attention (stimulus-driven reorienting) recruits
  a right lateralized ventral attention network in
  TPJ and VFC, in conjunction with the dorsal
  network.
• Detection of behaviorally relevant and novel
  stimuli
• Right hemisphere dominance during target
  detection is observed in regions that are
  frequently associated with neglect (IPL, STG,
  IFG) and for visual targets in both left and
  right hemi-field.
• Arousal and vigilance
• Neuroimaging studies of arousal and vigilance
  have qualitatively reported right hemisphere
  dominance. Arousal-related activations are
  recorded more frequently in ventral cortex of the
  right than left hemisphere
• Right Hemisphere lateralization of spatial
  deficits
• Most widely accepted standard theory is that
  right hemisphere controls shift of attention to
  both sides of space while the left hemisphere
  only controls attention to the right side.

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23.Explain the blue box and Figure 6
Detection
Reorienting
Arousal
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Right hemisphere dominance in vertebrates

• The lateralization of these processes is
  supported by similar findings in other species.
• The right hemisphere, the primary seat of
  emotional arousal, was at first specialized for
  detecting and responding to unexpected stimuli
  in the environment.
• Chicks
• Behavioral asymmetries arise partly from
  asymmetric light exposure prior to hatching
• Mammals
• Right hemisphere dominance for several nonspatial
  functions may partly reflect asymmetric brainstem
  projections.

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Dorsal vs. Ventral Spatial vs. Nonspatial
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1. Nonspatial function, such as arousal, is right
lateralized.

• 2. Increases in arousal bias attention to the
  left visual field, increasing left-field
  attention.

3. Ventral area ? Nonspatial function vs.
Dorsal area ? Spatial function
4. Right ventral area stroke patients have
non-spatial deficits (reduced vigilance and
slowness even in his right visual field), and
spatial neglects as well.
How are Ventral and Dorsal areas functionally
connected ?
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Dorsal vs. Ventral Spatial vs. Nonspatial
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1. The link between the damage to ventral
regions and the abnormal physiology of dorsal
regions.

• 2. Hypoactivation of the right hemisphere caused
  by ventral damage reduce interactions between the
  ventral and dorsal attention networks.

3. The result is unbalanced interhemispheric
physiological activity in the dorsal network
4. The right hemisphere dominance of neglect
follows from the specific biases produced by
right lateralized nonspatial mechanisms on the
direction of spatial attention.